Plants mostly glabrous, sparsely to densely pubescent basally along stem, trichomes to 2 mm. Stems (1.2-)2.5-6.5(-7.5) dm. Basal leaves (withered in fruit) laxly rosulate; petiole (0.5-)1-4 (-6) cm; blade spatulate, obovate, or oblong-oblanceolate, 0.5-3.5 cm × 6-20 mm, bases attenuate or cuneate, margins entire, repand, or sinuate-dentate, apex rounded. Cauline leaves: blade oblong, 1-4.5 cm × 2-10 mm, apex obtuse or subacute. Fruiting pedicels straight or slightly recurved, (6-)9-12(-16) mm. Flowers: sepals 1.2-2.6 × 0.7-1.2 mm; petals 2.5-4 × 1-1.7 mm, narrowed to clawlike base, apex obtuse; filaments 1.2-2 mm; anthers 0.2-0.4 mm. Fruits obovate or narrowly obcordate, 5-7.5 × 3.7-5.5 mm, base cuneate, apex shallowly emarginate, notch to 0.5 mm deep; wings obscure basally, to 1 mm wide apically; ovules 6-10 per ovary; style 0.1-0.3 mm. Seeds 1.2-1.4 × 0.9-1 mm, alveolate. 2n = 14.

Flowering Apr-May. Roadsides, grassy shoulders, fields, waste ground, pastures; 0-600 m; introduced; Del., Ind., Ky., La., Md., N.C., Ohio, Pa., Tenn., Va., W.Va.; Europe.

Thlaspi alliaceum has a garlic-like smell when fresh.